1. The Field of the Invention
The invention relates to cement compositions and products, and the methods of manufacturing and using such compositions. More particularly, the present invention is directed to novel magnesium oxychloride cement compositions, products, and uses thereof.
2. Review of the Technology
Cement and cementitious products affect everyone, from the roads we drive on, to the buildings we work in, to the homes we live in. Early principles and applications of cement and cement products were known anciently. The Romans, for example, developed cements and cement products to a high degree of sophistication. Despite centuries of knowledge concerning cements and cement products and despite countless variations of cement compositions, problems still arise while using cements which heretofore have not been adequately solved.
One of the most important uses of cement compositions is in concrete. As used herein, the term "concrete" is broadly defined as a hard strong building material made by mixing a water-cement mixture with a mineral aggregate such as sand and gravel. The cement acts as a glue to bind the aggregate particles together The physical properties of concrete vary depending on the cement composition and upon the choice of aggregates.
Concrete is commonly used to construct driveways, sidewalks, floors, and roads (hereinafter referred to generically as "road surfaces"). Concrete road surfaces are usually constructed of Portland cement. Although Portland cement is the industry standard, it is generally slow setting and requires a substantial cure time to reach an acceptable strength. In fact, it has been estimated that Portland cement does not reach full strength for about 100 years.
Despite careful selection of cement and aggregate, virtually all concrete road surfaces crack, chip, spall, or experience damage to one degree or another. The weather, the size and type of vehicles which travel on the road surfaces, as well as the quality of concrete and the skill in laying the concrete, influence the extent of damage to the concrete surface. In addition, reinforced concrete roads are often damaged when deicing salt is absorbed by the concrete. When the salt reaches the reinforcing steel, corrosion occurs, causing expansion and destruction of the road surface.
Once a concrete road surface is damaged, it is important to repair the damage in order to reduce the severity of future damage. Repairing damaged concrete surfaces, as referred to in this specification, implies restoring the damaged concrete surface to a state functionally equivalent to the undamaged state. The damaged surface may be patched, filled, resurfaced with thin or thick coatings, or restored in some other manner known in the art, depending on the circumstances and the type of damage.
There are many products on the market for repairing damaged concrete surfaces Historically, concrete was repaired by applying new concrete or mortar to the damaged area. This technique was not a long-term solution to the problem because the new concrete or mortar shrinks when it sets, thereby weakening or destroying the bond between the two surfaces.
In recent years, resin or epoxy-type materials have been used to repair damaged concrete surfaces. It was hoped that the resin cements with appropriate aggregates would solve the problems of traditional concrete repair compositions. Resin cements are fast setting and strong, but they are also expensive.
A common problem with epoxy-type cement compositions is that they set too fast, so fast that the epoxy-type cements have been known to harden before the user can properly apply and spread the composition over a damaged concrete surface. In addition, resin cements require the proper addition of special curing agents in order to adequately harden. Also, resin cements are adversely effected by ultraviolet rays which reduces their useful life. Unfortunately, even though such epoxy-type cements appear to form a good bond with the deteriorating road surface, it has been observed that the epoxy-type cements also fail with age and with heavy use.
Another important use of cement compositions is in exterior plaster and stucco applications, hereinafter referred to as stucco. Stucco is a popular exterior covering for residential and commercial buildings, particularly in the western United States. Historically, exterior stuccos have consisted of a Portland cement composition. Stucco wire or metal lath is usually placed over the exterior surface in order to support the cement stucco. In addition, paper or some other material is typically placed between the stucco composition and the substrate as a moisture barrier.
It is generally accepted that stucco applied directly to the substrate without wire or paper would crack and fail as the substrate expands, contracts, or bends due to the lack of adequate bond between the surface coating and the substrate. Multiple coats of the Portland cement stucco have been necessarily applied over a period of days with a normal curing time of five (5) days between coats in order to have a satisfactory product. Unfortunately, these cement stucco compositions tended to crack and shrink with age.
Moreover, when Portland cement stucco compositions are applied over a concrete block wall, the stucco composition "photographs" the mortar joints "Photographing" is a phenomenon which results because the mortar joints and concrete blocks absorb different amounts of water from the stucco composition. As a result, stucco applied over the mortar joints cures at a different rate than stucco applied over the concrete block. Consequently, stucco over the mortar joints has a different color than stucco over the concrete blocks.
In recent years, resin cement stuccos have been used instead of Portland cement stuccos. It was believed that these resin cement stuccos would overcome some of the problems associated with Portland cement stuccos. Unfortunately, it has been found that resin cement stuccos are subject to deterioration by heat and ultraviolet rays. Therefore, resin cement stuccos are subject to failure with age and exposure to the sun. In addition, the costs of construction using these resin cement stuccos can even surpass the costs of construction with brick veneer and commonly used exterior wall coverings.
Other examples illustrating additional uses of cement compositions would further demonstrate the need in the art for improved cement compositions. Nevertheless, from the foregoing, it will be appreciated that it would be a significant advancement in the art to provide cement compositions which possess a high structural strength, and yet have a high bonding strength to common substrates.
In addition, it will be appreciated that it would be an advancement in the art to provide relatively fast setting cement compositions which do not set so fast as to prevent adequate "working" of the compositions to form the desired product.
Additionally, it would be a further advancement in the art to provide cement compositions which do not shrink upon setting in order that a good bond can be formed with the adjacent surfaces, such as when used to repair deteriorating concrete road surfaces.
It would be yet another advancement in the art to provide cement compositions which are resistant to weather exposure, including heat, ultraviolet rays, and deicing salts.
It would be still another advancement in the art to provide cement compositions which do not require special curing compositions or techniques.
It would be an additional advancement in the art to provide cement stucco compositions which can be applied directly to a substrate surface without the need of costly stucco wire and without the need of labor intensive multiple coatings.
The foregoing, and other features and objects of the present invention are provided by the invention which is disclosed and claimed herein.